Enantioselective desymmetrization and parallel kinetic resolution of cyclopropanes via C–C activation: Synthesis of chiral β-lactams

Abstract

β-Lactams are privileged and appealing motifs in medicinal chemistry. Herein, we report enantioselective desymmetrization and parallel kinetic resolution of aminocyclopropanes for the synthesis of chiral β-lactams through Rh(I)-catalyzed asymmetric C–C bond activation. The chiral Rh(I) catalyzed C–C bond cleavage of aminocyclopropanes first and then underwent β-hydride elimination to generate π-allylic hydridorhodium(III) intermediates, which could be trapped by tethered alkyne units, and gave various strained chiral β-lactams with excellent regio- and enantioselectivity (90%–99% ee). Moreover, parallel kinetic resolution was realized when using unsymmetrical aminocyclopropanes with pre-existing C2-stereocenters through C–C bond activation, delivering two types of β-lactams in one pot with excellent enantiomeric excesses. Notably, these systems achieve complete atom and step economy. The obtained enantioenriched β-lactams exhibit the capability to undergo a variety of stereospecific transformations. Theoretical calculations reveal the origin of enantioselectivity and support the alkyne unit insertion to allylic Rh(III) –C bond mechanisms.